Iranian oil exports are on course to run well above the levels the Obama administration said they would when the U.S. agreed to allow some crude shipments in exchange for limits on Iran's domestic nuclear program.
Iran's exports are running at an average of 1.3 million barrels per day since December, about the time sanctions were eased. In comparison, its exports averaged only 1 million barrels a day in 2013 overall, with some months averaging as low as 850,000 barrels daily last year.
In November, the U.S. and five other countries agreed to a "Joint Plan of Action" for Tehran, and the administration has said repeatedly that Iran's oil exports would average only 1 million barrels per day for the first six months of that agreement.
For its part, the U.S. Treasury Department, which enforces sanctions against Iran, points out that those six months aren't yet over, and suggests that the averages will come down.
"I think it's important not to look at month-to-month fluctuations," said David Cohen, the Treasury's undersecretary for terrorism and financial intelligence. "Obviously we have figures that we're looking at very carefully as well. But the term under the Joint Plan of Action looks at oil sales over the course of the six months ... and calls upon Iran not to export over the course of six months more oil than they were exporting essentially last November."
But so far, at least, Iran appears to be doing just that. According to Nat Kern, analyst with Washington-based consulting firm Foreign Reports, Iranian exports to countries given purchase waivers by the U.S. government averaged 1.3 million barrels per day from December to April.
The Joint Plan of Action, announced in November, was signed Jan. 20, meaning that starting from that date, the U.S. officially began to monitor Iranian exports. Monitoring will continue through July. Given the exports from the first three months of the period, that means that May, June and July will have to show a sharp drop in oil exports in order for the total for the period to average out to the 1-million-barrel level.
When asked, Cohen said the U.S. is not intentionally looking the other way while Iran exceeds the export quota.
"We're not, and what I would say though is let's let the process run its course here," he said. "We are in the beginning of June. We still have more time on the clock here with the Joint Plan of Action, and we'll watch to see how things develop."
The sanctions program against Iran required a broad international agreement to cut off purchases of Iran's oil, but six countries were given waivers: Taiwan, Turkey, South Korea, Japan, India and China.
The exceptions were designed to give those nations time to find other supplies, but every six months they were to show that they were buying less crude from Iran. The program worked, and Iranian exports dropped from 2.7 million barrels per day to less than a million in 2013. The sanctions are widely credited with bringing Iran to the negotiating table last year.
But data show most of those countries are now importing more than they did last year; China, in particular, has been buying much more. According to Energy Aspects, Chinese imports from Iran spiked to a record high of 800,000 barrels per day in April. The previous high stood at around 650,000 barrels per day.
In a note to clients, Energy Aspects' chief oil analyst Amrita Sen wrote that the number "highlights the limited importance placed by China on the conditions of the U.S. sanctions waivers."
The State Department has offered a different explanation for the spike: Iran is exporting more "condensates"—byproducts of crude oil production that can be used to supplement a crude oil stream, Foreign Reports' Kern said in a presentation to clients.
The State Department said in April that condensates don't count toward the million barrels per day. Yet they were counted before, when Iranian exports were approaching 800,000 barrels per day.
Still, the success of the sanctions has emboldened the administration to use them as a tool against Russia as well, as that country ratchets up tension with Ukraine over its eastern provinces.
The sanctioning tactic was the subject of a day-long conference at the Center for Strategic and International Studies in Washington on Monday that was keynoted by Cohen.
"I think the key message today," Cohen told CNBC, "is that the tools the Treasury has developed over the past 10 years have been integrated into how we ... address serious foreign policy national security challenges, and how (we) continue to use those tools, modify those tools and continue to really use the leverage of the U.S. financial system, the U.S. economy, as a way to help us achieve really important national security objectives."
—By CNBC's Michelle Caruso-Cabrera